An alternating-current surface-discharging panel representing plasma display panels (hereinafter abbreviated as “panels”) has a large number of discharge cells formed between a front panel and rear panel faced with each other. In the front panel, a plurality of display electrodes, each made of a pair of scan electrode and sustain electrode, are formed on a front glass substrate in parallel with each other. A dielectric layer and a protective layer are formed to cover these display electrodes. In the rear panel, a plurality of parallel data electrodes is formed on a rear glass substrate. A dielectric layer is formed on the data electrodes to cover them. Further, a plurality of barrier ribs is formed on the dielectric layer in parallel with the data electrodes. Phosphor layers are formed on the surface of the dielectric layer and the side faces of the barrier ribs. Then, the front panel and the rear panel are faced with each other and sealed together so that the display electrodes and data electrodes intersect with each other. A discharge gas is filled into an inside discharge space formed therebetween. Discharge cells are formed in portions where respective display electrodes are opposed to corresponding data electrodes. In a panel structured as above, ultraviolet light is generated by gas discharge in each discharge cell. This ultraviolet light excites respective phosphors of R, G, and B colors, to emit respective colors for color display.
A general method of driving a panel is a sub-field method: one field period is divided into a plurality of sub-fields and combination of light-emitting sub-fields provides gradation display. Among the sub-field method, a novel driving method of minimizing the light emission unrelated to gradation display to inhibit an increase in black picture level and improve a contrast ratio is disclosed in Japanese Patent Unexamined Publication No. 2000-242224.
The driving method is briefly described hereinafter. Each sub-field has an initializing period, writing period, and sustaining period. In the initializing period, one of all-cell initializing operation and selective initializing operation is performed. The all-cell initializing operation causes initializing discharge in all the discharge cells for image display. The selective discharge operation selectively causes initializing discharge in the discharge cells subjected to sustaining discharge in the preceding sub-filed.
First, in the all-cell initializing period, all the discharge cells perform initializing discharge operation at a time, to erase the history of wall electric charge previously formed in respective discharge cells and form wall electric charge necessary for the subsequent writing operation. Additionally, this initializing discharge operation serves to generate priming (priming for discharge=excited particles) for reducing discharge delay and causing stable writing discharge. In the subsequent writing period, scan pulses are sequentially applied to scan electrodes, and write pulses corresponding to the signals of an image to be displayed are applied to data electrodes. Thus, selective writing discharge is caused between the scan electrodes and corresponding data electrodes to selectively form wall electric charge. In the sustaining period, a predetermined number of sustain pulses according to a brightness weight is applied between the scan electrodes and corresponding sustain electrodes. Then, the discharge cells in which wall electric charge has been formed by the writing discharge are selectively discharged so that light is emitted from the discharge cells.
In this manner, to properly display an image, selective writing discharge must securely be performed in the writing period. For this purpose, ensuring initializing operation, i.e. preparation for the writing operation, is important.
In the all-cell initializing operation, it is necessary to cause initializing discharge using the scan electrodes as anodes and the sustain electrodes and data electrodes as cathodes. However, phosphors having smaller electron emission factors that are applied to the data electrodes may increase discharge delay in the initializing discharge using the data electrodes as cathodes, thus causing unstable initializing discharge in some cases.
Additionally, considerations have recently been given to increasing the partial pressure of xenon in the discharge gas filled into the panel to improve the luminous efficiency of the panel. However, an increase in the partial pressure of xenon destabilizes discharge, especially initializing discharge. This unstable discharge poses a problem of writing failure in the subsequent writing period that is caused by a narrower margin of the driving voltage in the wiring operation.
The present invention addresses these problems and aims to provide a method of driving a panel in which stabilization of initial discharge allows images to be displayed in excellent quality.